A) A lot of the people on these forums should probably be banned for excessive whining. It would greatly improve the quality of discourse.
B) You will most likely enjoy playing Brawl. Your whining about characters notwithstanding, the reality is that it is most likely a fun game and there is no reason they needed a 50+ character cast; indeed, a 50+ character cast would almost certainly mean a lot of broken/terrible characters. 37-39 characters is already a lot.
C) This is a game, we play it for fun. Random people will pick it up and not be like "Oh, it sucks that <obscure/irrelevant character from pet francise X> isn't in this game"; they'll be like "Oh, wow, I can beat up Snake with Mario!".
D) Who were the notable omissions? Mewtwo is not as important as Pikachu; any pokemon beyond Pikachu is bound to be random. We've got representatives from the most important Nintendo francises plus several random characters and the awesomeness that is Sonic and Snake. I mean, you go down the list of famous Nintendo characters, all of the top ones are in. I don't know who Ridley is, but I know who Samus is. I know who all the major Zelda characters are. ect. Why the complaints?
Basically, they included characters they thought would be fun and interesting, and that is all that should be asked for. If you don't like it, quit whining about it. Just don't buy the game if you disapprove so strongly.
But of course you don't. You're just whining for the sake of whining. Whining about the cast is pointless; its a fine cast and is +11-13 larger than that of SSBM, and more than three times the cast of the original game. We get about +12 characters per game, and that is a LOT of characters to add; if they're all cool, then that's a good game, and if they're all balanced, that's an amazing one.
Its not like they limit the cast to spite you. They limit it for good reasons. Quit your whining. This is as many characters as was reasonable to expect, and the cast inflation is getting a bit crazy.
Also, as for those of you saying this will be the last Super Smash Brothers game: you're wrong. There will be another one for the next system, ect. There are many things Nintendo does and does not do. Nintendo will never just let a successful francise go. Seriously. This sold 500,000 copies on DAY 1. There will be another Smash Brothers game someday. Nintendo will never let it die until it no longer sells. How many Mario platformer games are there?